In a Long Term Evolution (LTE) system, after receiving downlink data sent by a network device, a terminal device needs to send hybrid automatic repeat request-acknowledgement (HARQ-ACK) feedback information to the network device. If the downlink data is correctly received, the terminal device returns acknowledgement (ACK) information; if the downlink data is not correctly received, the terminal device returns non-acknowledgement (NACK) information. The HARQ-ACK feedback information may be carried on a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH).
In a wireless communications system, a latency is one of important factors affecting user experience. In addition, emerging of new services, such as a related service of the Internet of Vehicles, imposes an increasingly harsh requirement on a low latency. Therefore, in an existing LTE system, a transmission mechanism based on a one-subframe transmission time interval (TTI) cannot meet a demand for a low-latency service. How to reduce a latency becomes a problem to be resolved urgently.